The present invention relates to mobile communications, and more particularly, to different services and features that may be employed to establish and enhance communications between a mobile station in a mobile communications network and an external network entity.
The main application of most mobile radio systems like the Global System for Mobile communications (GSM) has been mobile telephony which typically only supports circuit-switched communications where guaranteed, xe2x80x9cfixedxe2x80x9d circuits are dedicated to a user for the duration of a call. However, packet-switched applications, like facsimile transmission and short message exchange, are becoming popular in mobile networks. Example data applications include wireless personal computers, mobile offices, electronic funds transfer, road transport telemetry, field service businesses, fleet management, etc. These data applications are characterized by xe2x80x9cburstyxe2x80x9d traffic where a relatively large amount of data is transmitted over a relatively short time interval followed by significant time intervals when little or no data is transmitted.
While bursty traffic can be transmit using a circuit-switched channel, such a transmission underutilizes that channel because there are likely large intervals between bursts when the channel is reserved but is not being used, there is no information to be transmit from or received by the user. From an efficiency view point, this is a waste of transmission resources which are particularly limited for radio communications. However, from a customer service view point, because a circuit-switched channel is not shared with other users, the user is essentially guaranteed a certain quality of service. In addition to inefficiency, it takes a relatively long time to set up and take down a circuit-switched call compared with individual packet routing in packet-switched sessions. In bursty traffic situations, packet-switched bearers better utilize the transmission bandwidth because a communications resource is used only when there is data to transmit. Communication channels are therefore typically shared by many users. Another advantage is that in contrast to time-oriented charging applied for circuit-switched connections, packet-switched data services allow charging depending on the amount of data actually transmitted and on the quality of service of that transmission.
In order to provide such mobile data applications, packet radio network services accommodate connectionless, packet-switched data services with high bandwidth efficiency. One example is the General Packet Radio Service (GPRS) incorporated into the existing circuit-switched GSM network. Another is the Cellular Digital Packet Data (CDPD) network used into the existing D-AMPS network. A significant interest of end users of a mobile packet data service such as GPRS is that wireless PCs support conventional Internet-based applications like file transfer, submission and reception of e-mail, and xe2x80x9csurfingxe2x80x9d the Internet via the worldwide web. Conferencing and playback applications, including video and multimedia, are also important services to be supported by mobile networks.
Although circuit-switched services are well known in mobile networks, mobile packet-switched services are quite new. Therefore, a brief description of the latter using GSM/GPRS as an example is now provided.
FIG. 1 shows a mobile data service from a user""s point of view in the context of a mobile communications system 10. An end user communicates data packets using a mobile host 12 including for example a laptop computer 14 connected to a mobile terminal 16. The mobile host 12 communicates for example with a fixed computer terminal 18 incorporated in a local area network (LAN) 20 through a mobile packet data support node 22 via one or more routers 24, a packet data network 26, and a router 28 in the local area network 20. Of course, those skilled in the art will appreciate that this drawing is simplified in that the xe2x80x9cpathxe2x80x9d is a logical path rather than an actual physical path or connection. In a connectionless data packet communication between the mobile host 12 and fixed terminal 18, packets are routed from the source to the destination independently and do not necessarily follow the same path (although they can).
Thus, independent packet routing and transfer within the mobile network is supported by a mobile packet data support node 22 which acts as a logical interface or gateway to external packet networks. A subscriber may send and receive data in an end-to-end packet transfer mode without using any circuit-switched mode network resources. Moreover, multiple point-to-point, parallel applications are possible. For example, a mobile host like a mobile PC might run at the same time a video conference application, an e-mail application, a facsimile application, a web browsing application, etc. The video conference application would typically require more than one data stream (hereafter referred to as an application flow).
FIG. 2 shows a more detailed mobile communications system using the example GSM mobile communications model that supports both circuit-switched and packet-switched communications and includes a circuit-switched network 35 and a packet-switched network 51. A mobile host 12 including a computer terminal 14 and mobile radio 16 communicates over a radio interface with one or more base stations (BSs) 32. Each base station 32 is located in a corresponding cell 30. Multiple base stations 32 are connected to a base station controller (BSC) 34 which manages the allocation and deallocation of radio resources and controls handovers of mobile stations from one base station to another. A base station controller and its associated base stations are sometimes referred to as a base station subsystem (BSS). The BSC 34 is connected to a mobile switching center (MSC) 36 in the GSM circuit-switched network 35 through which circuit-switched connections are set up with other networks 38 such as the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), etc.
The MSC 36 is also connected via a Signaling System Number 7 (SS7) network 40 to a Home Location Register (HLR) 42, a Visitor Location Register (VLR) 44, and Authentication Center (AUC) 46. The VLR 44 includes a database containing the information about all mobile stations currently located in a corresponding location or service area as well as temporary subscriber information needed by the MSC to provide services to mobiles in its service area. Typically, when a mobile station enters a visiting network or service area, the corresponding VLR 44 requests and receives data about the roaming mobile station from the mobile""s HLR and stores it. As a result, when the visiting mobile station is involved in a call, the VLR 44 already has the information needed for call setup.
The HLR 42 is a database node that stores and manages subscriptions. For each xe2x80x9chomexe2x80x9d mobile subscriber, the HLR contains permanent subscriber data such as the mobile station ISDN number (MSISDN) which uniquely identifies the mobile telephone subscription in the PSTN numbering plan and an international mobile subscriber identity (IMSI) which is a unique identity allocated to each subscriber and used for signaling in the mobile networks. All network-related subscriber information is connected to the IMSI. The HLR 42 also contains a list of services which a mobile subscriber is authorized to use along with a current subscriber location number corresponding to the address of the VLR currently serving the mobile subscriber.
Each BSC 34 also connects to the GSM packet-switched network corresponding to GPRS network 51 at a Serving GPRS Support Node (SGSN) 50 responsible for delivery of packets to the mobile stations within its service area. The gateway GPRS support node (GGSN) 54 acts as a logical interface to external data packet networks such as the IP data network 56. SGSN nodes 50 and GGSN nodes 54 are connected by an intra-PLMN IP backbone 52. Thus, between the SGSN 50 and the GGSN 54, the Internet protocol (IP) is used as the backbone to transfer data packets.
Within the GPRS network 51, packets or protocol data units (PDUs) are encapsulated at an originating GPRS support node and decapsulated at the destination GPRS support node. This encapsulation/decapsulation at the IP level between the SGSN 50 and the GGSN 54 is called xe2x80x9ctunnelingxe2x80x9d in GPRS. The GGSN 54 maintains routing information used to xe2x80x9ctunnelxe2x80x9d PDUs to the SGSN 50 currently serving the mobile station. A common GPRS Tunnel Protocol (GTP) enables different underlying packet data protocols to be employed even if those protocols are not supported by all of the SGSNs. All GPRS user-related data needed by the SGSN to perform routing and data transfer functions is accessed from the HLR 42 via the SS7 network 40. The HLR 42 stores routing information and maps the IMSI to one or more packet data protocol (PDP) addresses as well as mapping each PDP address to one or more GGSNs.
Before a mobile host can send packet data to an external network like an Internet service provider (ISP) 58 shown in FIG. 2, the mobile host 12 has to (1) xe2x80x9cattachxe2x80x9d to the GPRS network 51 to make its presence known and (2) create a packet data protocol (PDP) context to establish a relationship with a GGSN 54 towards the external network that the mobile host is accessing. The attach procedure is carried out between the mobile host 12 and the SGSN 50 to establish a logical link. As a result, a temporary logical link identity is assigned to the mobile host 12. A PDP context is established between the mobile host and the GGSN 54. The selection of a GGSN 54 is based on the name of the external network to be reached.
One or more application flows (sometimes called xe2x80x9crouting contextsxe2x80x9d) may be established for a single PDP context through negotiations with the GGSN 54. An application flow corresponds to a stream of data packets distinguishable as being associated with a particular host application. An example application flow is an electronic mail message from the mobile host to a fixed terminal. Another example application flow is a downloaded graphics file from a web site. Both of these application flows are associated with the same mobile host and the same PDP context.
Packet-switched data communications are based on specific protocol procedures which are typically separated into different layers. FIG. 3A shows a GPRS xe2x80x9ctransmission planexe2x80x9d that is modeled with multi-layer protocol stacks. Between the GGSN and the SGSN, the GPRS tunneling protocol (GTP) tunnels the PDUs through the GPRS backbone network 52 by adding routing information to encapsulate PDUs. The GTP header contains a tunnel end point identifier (TID) for point-to-point and multicast packets as well as a group identity (GID) for point-to-multipoint packets. Additionally, a type field that specifies the PDU type and a quality of service profile associated with a PDP context session is included. Below the GTP, the well-known Transmission Control Protocol/User Diagram Protocol (TCP/UDP) and Internet Protocol (IP) are used as the GPRS backbone network layer protocols. Ethernet, frame relay (FR), or asynchronous transfer mode (ATM)-based protocols may be used for the link and physical layers depending on the operator""s network architecture.
Between the SGSN and mobile station/host, a SubNetwork Dependent Convergence Protocol (SNDCP) maps network level protocol characteristics onto the underlying logical link control (LLC) and provides functionalities like multiplexing of network layer messages onto a single virtual logical connection, ciphering, segmentation, and compression. A Base Station System GPRS Protocol (BSSGP) is a flow control protocol, which allows the base station system to start and stop PDUs sent by the SGSN. This ensures that the BSS is not flooded by packets in case the radio link capacity is reduced, e.g., because of fading and other adverse conditions. Routing and quality of service information are also conveyed. Frame relay and ATM may be used to relay frames of PDUs over the physical layer.
Radio communication between the mobile station and the GPRS network covers physical and data link layer functionality. The physical layer is split up into a physical link sublayer (PLL) and a physical RF sublayer (RFL). RFL performs modulation and demodulation of the physical waveforms and specifies carrier frequencies, radio channel structures, and raw channel data rates. PLL provides services for information transfer over the physical radio channel and includes data unit framing, data coding, and detection/correction of physical medium transmission areas. The data link layer is separated into two distinct sublayers. The radio link control/medium access control (RLC/MAC) sublayer arbitrates access to the shared physical radio medium between multiple mobile stations and the GPRS network. RLC/MAC multiplexes data and signaling information, performs contention resolution, quality of service control, and error handling. The logical link control (LLC) layer operates above the MAC layer and provides a logical link between the mobile host and the SGSN.
It is important to be able to provide a certain particular communications service with a requested quality. For example, certain multimedia applications or even a simple voice phone call need guarantees about accuracy, dependability, and speed of transmission. In packet-switched communications, xe2x80x9cbest effortsxe2x80x9d are usually employed, and no special attention is paid to delay or throughput guarantees. Generally, quality of service parameters can be characterized qualitatively in three services classes including deterministic (used for hard, real-time application), statistical (used for soft real-time applications), and best effort (everything else where no guarantees are made). Quantitative parameters may include throughput (such as the average data rate or peak data rate), reliability, delay, and jitter corresponding to the variation delay between a minimum and maximum delay time that a message experiences.
In the context of providing quality of service (QoS) in a mobile data communications systems, one QoS approach is to assign a specific priority to each PDP context. But this approach is unsatisfactory. As explained above, each PDP context may have plural application flows, and each application flow may have different needs. For example, real time applications like telephony require a guaranteed, low delay service while image video needs a predictable delay service. More specifically, elastic applications like interactive bursts, interactive bulk transfer, and asynchronous bulk transfer require different degrees of best effort or as soon as possible delay service.
It is an important objective of the present invention to provide quality of service based, radio Internet access in order to support multiple application services including voice, data, and multimedia, where some of the applications may have plural application flows operating simultaneously. In the case of Internet integrated services, important quality of service factors are perceived transport link layer delay, jitter, bandwidth, and reliability. Rather than limiting the quality of service to a single PDP context, the present invention defines a quality of service for each individual application flow as is described below and in the above-identified patent application. In addition, the present invention permits selection of a particular type of transfer mechanism that is best suited to transfer the individual application flow in accordance with its quality of service requirements.
Normally a network technology transfers data only according to one type of transfer mechanismxe2x80x94either circuit-switched or packet-switchedxe2x80x94even in the GSM which includes both a circuit-switched and a packet-switched network sharing the same radio access interface. In the present invention an optimal type of mobile communications network transfer servicexe2x80x94a circuit-switched transfer service or a packet-switched transfer servicexe2x80x94is specified on an individual application flow basis. Circuit-switched services may be selected, for example, for real time (low delay and small jitter) application flows like audio and video. Packet-switched bearers may be selected for non-real time, Internet type data applications such as surfing on the worldwide web, file transfer, e-mail, and telnet, all of which require fast channel access and bursty data transfer capability.
Initially a mobile station registers with the mobile communications network to establish communication with an external network entity such as an Internet service provider (ISP). During that communication, an application may initiate different data streams or flows of an application (hereafter referred to as application flows) between the mobile station and the external network entity. For each application flow, a determination is made whether a circuit-switched or a packet-switched bearer should be established. A bearer xe2x80x9cbearsxe2x80x9d or carries information from the mobile station through the mobile communications network towards the external network entity and carries information from the external network entity through the mobile communications network to the mobile station.
Each application flow may have a corresponding quality of service request. Based on that corresponding quality of service, a determination is made whether a circuit-switched bearer or a packet-switched bearer is better suited to transport the application flow. The quality of service parameters specified by the application for an individual application flow are mapped to corresponding quality of service parameters for the selected one of the circuit-switched or packet-switched bearers. Mobile communication resources for the selected bearer and corresponding quality of service parameters may be reserved in advance for each application flow (the resource reservation approach). Alternatively, the header of each information packet in an application flow may specify a generally recognized class of service which when read determines whether a circuit-switched bearer or a packet-switched bearer carries that packet (the differential services approach).
Various algorithms may be used to determine the type of bearer to be allocated to specific application flows. For example, a determination may be made whether an application flow requests a real time service or a non-real time service. A circuit-switched bearer is allocated if the request is for a real time service, and a packet-switched bearer is allocated if the request is for a non-real time type of service. Other criteria may be employed. For example, a circuit-switched bearer may be allocated if the application flow requests low delay or small jitter per packet, and a packet-switched bearer may be allocated if the application flow requests fast channel access or bursty data transfer capability. Yet another example approach may be to determine for each application flow an amount of information to be sent and/or its flow duration. A circuit-switched bearer may be allocated if a large amount of information is to be sent or if the application flow has a long life-time. Otherwise, a packet-switched bearer would be allocated.
In any bearer allocation approach, it is preferred (but not required) that a packet-switched bearer be employed to carry control information being bursty and brief by nature and because of the fast set up and take down times afforded by packet-switched bearers. On the other hand, if a circuit-switched bearer to a mobile station already exists for an application flow, packet-switched type information can be transferred over the existing circuit-switched bearer (because it is existing) even if that information is more suitable for transfer over a packet-switched type bearer. This approach is used, for example, with mobile stations that cannot terminate simultaneous circuit-switched and packet-switched traffic, e.g., so-called class B GPRS mobile stations.
A significant advantage of the present invention is that applications running on a mobile station or on an external network entity such as an Internet service provider may specify on an individual application flow basis a requested quality of service, and with this information, select the type of bearer to be employed when transferring the application flow through the mobile communications network. Both the quality of service characteristics for an application flow and the type of bearer/transfer mechanism can be selected at the application layer which is advantageous because the application has the best end-to-end perspective of the communication.
The mobile station and a mobile network gateway node each include a mapper for mapping individual application flows to one of the circuit-switched network and the packet-switched network bearers depending on the quality of service requested for an individual application flow. Quality of service parameters corresponding to an individual application flow are also mapped to circuit-switched parameters if the application flow is mapped to the circuit-switched network and to packet-switched parameters if the application flow is mapped to the packet-switched network.
The gateway node includes a common access server which permits a mobile station initially establishing a communications session with an external network entity to perform only a single common access procedure for subsequent communications using either the circuit-switched network or the packet-switched network. After that common access procedure is completed, subsequent application flows between the mobile station and the external network entity are established without having to perform another access procedure involving the external network entity.
The common access procedure includes a common authentication procedure for authenticating the identity of the mobile station with the external network entity. Thereafter, the mobile station is authorized for subsequent application flows with the external network entity for both of the circuit-switched and packet-switched networks. The common authentication procedure includes confirming a mobile station identification and password to determine whether the mobile station is authorized to communicate with the external network entity.
The common access procedure also employs a common configuration procedure for configuring the mobile station with the external network entity. Thereafter, the mobile station is configured with a common network address for subsequent application flows with the external network entity for both of the circuit-switched and packet-switched networks. The common configuration procedure includes providing the mobile station with parameters needed to communicate with the external network entity including the network layer address allocated to the mobile station. The configuration parameters are stored by the common access server so that for subsequent application streams involving the mobile station during the session, the common access server retrieves the stored parameters and configures the subsequent application stream without involving the external network entity.
By permitting individual application flows to individually select (1) quality of service parameters and (2) type of transfer mechanism (either circuit-switched or packet-switched bearer), the present invention provides better service for different types of applications. At the same time, the common access procedure for all application flows in a session provides much faster service. Indeed, authentication and configuration procedures between a mobile station and an Internet service provider may take on the order of twenty to thirty seconds to perform when using a circuit-switched bearer. This significant delay is even more onerous if such access procedures must be performed for each of multiple application flows. Consider the length of the delay associated with a conferencing application that requires simultaneous execution of multiple application flows.
These onerous delays are eliminated in the present invention. At mobile registration, an initial authentication and configuration procedure using a packet-switched bearer is performed in less than half the 20 to 30 seconds noted above. Even more time is saved because this initial authentication and configuration procedure is not performed for each subsequent individual application flow. Instead, abbreviated authentication and configuration procedures are performed for subsequent flows contained within the mobile communications network at the common access server in just a few seconds.